Waste gas purification apparatus and method therefor

ABSTRACT

A waste gas purification apparatus comprises a cooling unit including a cooling chamber containing a cooling fluid and a waste gas transmission pipe passing through the cooling chamber and immersing in the cooling fluid, which is used to cool the waste gas input into the waste gas transmission pipe; a dust eliminating unit provided at the downstream side of the cooling unit and used to eliminate harmful substances and dust contained in the waste gas; an absorbing unit provided at the downstream side of the dust eliminating unit and containing an absorbing fluid, which is used to eliminate carbon dioxide and sulfide contained in the waste gas by mean of the reaction between the absorbing fluid and the carbon dioxide and sulfide, in which the carbon dioxide and sulfide react with the absorbing fluid to generate precipitates; and a cleaning unit provided at the downstream side of the absorbing unit and containing a cleaning fluid, which is used to eliminate harmful substances and dust remained in the waste gas. A waste gas purification method is also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority benefit of Chinese patent application No. CN200710092120.9 filed on Apr. 20, 2007, the content of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to an apparatus and method for purifying waste gas, in particular to an apparatus and method for purifying waste gas, which could purify the waste gas by eliminating dust, carbon dioxide, sulfide and other harmful substances contained in the waste gas.

BACKGROUND OF THE INVENTION

With the development of the society, the environmental protection sense of human being is increasingly improved. However, to obtain more energy, people have to burn more and more mineral fuel, petroleum products and organic substances, which continuously generate waste gas containing a large amount of dust, carbon dioxide, sulfide and other harmful substances, such as dioxin (PCDD), TCDD and etc. The dust in the waste gas would deteriorate air quality. The carbon dioxide would incur greenhouse effect resulting in global climate warming. The sulfide would generate acid rain resulting in soil acidification and soil erosion, which will affect the growth of plants. The harmful substances such as PCDD and TCDD are in form of particle under normal temperature, which are very easy to accumulate in the organism, thus it is very difficult to eliminate PCDD and TCDD from the natural environment by mean of natural degradation. All of the above-mentioned substances are criminals of climate warming and environment deterioration. However, till now, there is not a single waste gas purification apparatus with simple structure, which is capable of efficiently purifying waste gas exhausted from a burning furnace.

SUMMARY OF THE INVENTION

To overcome the above-mentioned questions, the present invention provides a waste gas purification apparatus, which comprises a cooling unit including a cooling chamber containing a cooling fluid and a waste gas transmission pipe passing through the cooling chamber and immersing in the cooling fluid, which is used to cool the waste gas input into the waste gas transmission pipe; a dust eliminating unit provided at the downstream side of the cooling unit and used to eliminate harmful substances and dust contained in the waste gas; an absorbing unit provided at the downstream side of the dust eliminating unit and containing an absorbing fluid, which is used to eliminate carbon dioxide and sulfide contained in the waste gas by mean of the reaction between the absorbing fluid and the carbon dioxide and sulfide, in which the carbon dioxide and sulfide react with the absorbing fluid to generate precipitates; and a cleaning unit provided at the downstream side of the absorbing unit and containing a cleaning fluid, which is used to eliminate harmful substances and dust remained in the waste gas.

The cooling chamber may be provided with a cooling fluid level adjustment device for adjusting the level of the cooling fluid contained in the cooling chamber, to immerse the waste gas transmission pipe in the cooling fluid all the time. In addition, the cooling chamber may be a hermetic container and provided with a steam recycling device for recycling the steam generated by the cooling fluid during the course of cooling the waste gas.

Preferably, a pumping device may be provided between the dust eliminating unit and the absorbing unit, which is used to pump the waste gas output from the dust eliminating unit to the inside bottom part of the absorbing unit to enable the waste gas to be released under the level of the absorbing fluid.

Preferably, the apparatus of the present invention further comprises a waste gas tank provided at the upstream side of the waste gas cooling unit, which is used to let the waste gas rest therein to remove large dust particles contained in the waste gas before the waste gas is supplied to the waste gas transmission pipe.

In another aspect, the present invention provides a waste gas purification method, which comprises: a cooling step for cooling the waste gas; a dust eliminating step for eliminating harmful substances and dust contained in the waste gas after the waste gas is processed in the cooling step; an absorbing step for eliminating carbon dioxide and sulfide contained in the waste gas after the waste gas is processed in the dust eliminating step; and a purifying step for eliminating harmful substances and dust remained in the waste gas after the waste gas is processed in the absorbing step.

The cooling step may further comprise a steam recycling step for recycling the steam generated in the cooling step. The absorbing step may further comprise an absorbing fluid purifying step for removing precipitates generated in the absorbing step and for recharging absorbing fluid.

Preferably, the method of the present invention may further comprises a resting step for letting the waste gas rest to remove large dust particles contained in the waste gas before the waste gas is processed in the cooling step.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a front cross-sectional view of an embodiment of the waste gas purification apparatus according to the present invention; and

FIG. 2 is a top cross-sectional view of the embodiment shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, the waste gas purification apparatus of the present invention comprises a cooling unit 2, a dust eliminating unit 5 and an absorbing unit 15. The cooling unit 2 includes a cooling chamber 12 containing cooling fluid 3 such as cooling water, and a waste gas transmission pipe 21 passing through the cooling chamber 12, through which the high temperature waste gas is transmitted. The waste gas transmission pipe 21 is immersed in the cooling fluid 3, to enable heat exchanging between the high temperature waste gas transmitted within the transmission pipe and the cooling fluid outside the transmission pipe, to cool the high temperature waste gas. Alternatively, a plurality of waste gas transmission pipes 21 may be provided in the cooling chamber 12. As shown in FIG. 2, there are three waste gas transmission pipes 21 provided in the cooling chamber 12, and each of them is immersed in the cooling fluid. The cooling chamber 12 may also be provided with a cooling fluid level adjustment device 4, which is used to adjust the level of the cooling fluid contained in the cooling chamber to enable immersing the waste gas transmission pipes 21 in the cooling fluid all the time. The cooling fluid level adjustment device 4 is connected to a cooling fluid supply. When part of the cooling fluid is consumed, which may cause the waste gas transmission pipe to be exposed out of the level of the cooling fluid, the level adjustment device 4 is turned on to supply cooling fluid into the cooling chamber. Thus, the waste gas transmission pipe could be submerged in the cooling fluid.

In addition, the cooling chamber 12 may be a hermetic container and be provided with a steam recycling device 14, to recycle the steam generated by the cooling fluid during the course of cooling the high temperature waste gas. For example, the recycled steam may be used to generate power. The cooling chamber may be separated into a plurality of compartments by a plurality of spacers, and a steam communication port 13 may be provided at the upper part of each spacer, to enable the steam to communicate between adjacent compartments. A cooling fluid communication port 41 may be provided at the lower part of each spacer, to enable the cooling fluid to communicate between adjacent compartments. However, each of the compartments may be separated from each other at their lower parts and be provided with their respective cooling fluid level adjustment device. Thus, the compartments may contain different kinds of cooling fluids and/or cooling fluids with different temperatures, to enable subsection cooling of the high temperature waste gas.

The harmful substances contained in the waste gas, such as dioxin (PCDD), TCDD have a melting point of about 88° C. to 330° C., and are solid under normal temperature. To eliminate those harmful substances, the cooled waste gas is supplied into the dust eliminating unit 5 provided at the downstream side of the cooling unit 2. The dust eliminating unit 5 may be any kind of dust eliminating unit known in the prior art. The dust eliminating unit 5 further cools the waste gas to normal temperature or any other temperature suitable for eliminating PCDD and TCDD, to make PCDD and TCDD contained in the waste gas to transform to solid particles. Thus, PCDD and TCDD could be eliminated from the waste gas together with dusts suspending in the waste gas.

After being processed in the dust eliminating unit, the waste gas is supplied to the absorbing unit 15 provided at the downstream side of the dust eliminating unit 5, to eliminate carbon dioxide and sulfide contained in the waste gas. The absorbing unit 15 is a hermetic container, which contains absorbing fluid 7, such as alkaline solution. For example, calcium hydroxide solution could be used as absorbing fluid for absorbing carbon dioxide and sulfide. When the waste gas is supplied to the calcium hydroxide solution, the carbon dioxide and sulfide contained in the waste gas will react with calcium hydroxide to generate precipitates, thus, the carbon dioxide and sulfide would be eliminated from the waste gas. A pumping device 6 may be provided between the dust eliminating unit 5 and the absorbing unit 15 and be used to pump the waste gas output from the dust eliminating unit 5 to the inside bottom part of the absorbing unit 15, which could make the waste gas to be released under the level of the absorbing fluid to improve the efficiency of eliminating carbon dioxide and sulfide.

In addition, to further improve the efficiency of eliminating carbon dioxide and sulfide, the purification apparatus of the present invention may comprise a plurality of absorbing units provided in series. For example, two absorbing unit are provided in the embodiment shown in FIG. 1. The waste gas output from the former absorbing unit is supplied to the latter absorbing unit, to further eliminate the carbon dioxide and sulfide contained in the waste gas. Similarly, a pumping device may be provided between adjacent absorbing units, to improve the efficiency of eliminating carbon dioxide and sulfide.

As shown in FIG. 2, the absorbing unit 15 may be provided with an absorbing fluid refreshing device 17. The absorbing fluid refreshing device 17 could be used to remove the precipitates in the absorbing unit 15 and recharge absorbing fluid into the absorbing unit 15, to maintain the absorbing capacity of the absorbing unit 15.

A cleaning unit 16 may be provided at the downstream side of the absorbing unit 15. The cleaning unit 16 contains cleaning fluid 8, such as clean water. The waste gas is supplied to the cleaning unit 16 after being processed by the absorbing unit 15, to further eliminate the dust and harmful substances remained in the waste gas.

A detection unit 10 may be provided at the downstream side of the cleaning unit 16 to detect whether or not the waste gas is purified. The waste gas is supplied to the detection unit 10 through an output port 9 after being cleaned by the cleaning unit 16. The waste gas is discharged to the air after being detected to be qualified.

The purification apparatus of the present invention may also be provided with a waste gas tank 1. The waste gas tank 1 is a hermetic container, which is provided at the upstream side of the waste gas cooling unit 2 and between the waste gas transmission pipe 21 and waste gas source (not shown in the figures). Before the waste gas is supplied to the waste gas transmission pipe 21, it could rest in the waste gas tank 1, to remove large dust particles, therefore, the purification load of the other units of the purification apparatus could be alleviated.

According to the above description and referring to FIGS. 1 and 2, the purification method of the present invention will be described, which mainly comprises a cooling step, in which the high temperature waste gas is cooled in the cooling unit 2; a dust eliminating step, in which the cooled waste gas is input to the dust eliminating unit 5 so as to transform the harmful substances contained in the waste gas to solid particles and to remove the solid particles of the harmful substances and dust suspending in the waste gas; an absorbing step, in which the waste gas is input into the absorbing fluid contained in the absorbing unit 15, to absorb the carbon dioxide and sulfide contained in the waste gas; and a cleaning step, in which the waste gas is input to the cleaning unit 16 to finally clean the waste gas by the cleaning fluid 8.

The purification method may also comprising a resting step, in which the high temperature waste gas rests in the waste gas tank 1 before proceeding to the cooling step, to remove large dust particles from the waste gas.

Through the waste gas purification apparatus and purification method of the present invention, the dust, carbon dioxide, sulfide and harmful substances such as dioxin (PCDD), TCDD and etc. contained in the waste gas exhausted from a burning furnace could be effectively eliminated, therefore, the environmental pollution of the waste gas exhausted from a power plant, garbage incinerator or metallurgical plant could be reduced effectively. 

1. A waste gas purification apparatus comprising: a cooling unit including a cooling chamber containing a cooling fluid and a waste gas transmission pipe passing through the cooling chamber and immersing in the cooling fluid, which is used to cool the waste gas input into the waste gas transmission pipe; a dust eliminating unit provided at the downstream side of the cooling unit and used to eliminate harmful substances and dust contained in the waste gas; an absorbing unit provided at the downstream side of the dust eliminating unit and containing an absorbing fluid, which is used to eliminate carbon dioxide and sulfide contained in the waste gas by mean of the reaction between the absorbing fluid and the carbon dioxide and sulfide, in which the carbon dioxide and sulfide react with the absorbing fluid to generate precipitates; and a cleaning unit provided at the downstream side of the absorbing unit and containing a cleaning fluid, which is used to eliminate harmful substances and dust remained in the waste gas.
 2. The waste gas purification apparatus according to claim 1, wherein the cooling chamber is provided with a cooling fluid level adjustment device for adjusting the level of the cooling fluid contained in the cooling chamber, to immerse the waste gas transmission pipe in the cooling fluid all the time.
 3. The waste gas purification apparatus according to claim 1, wherein the cooling chamber is a hermetic container and provided with a steam recycling device for recycling the steam generated by the cooling fluid during the course of cooling the waste gas.
 4. The waste gas purification apparatus according to claim 2, wherein the cooling chamber is a hermetic container and provided with a steam recycling device for recycling the steam generated by the cooling fluid during the course of cooling the waste gas.
 5. The waste gas purification apparatus according to claim 3, wherein the cooling chamber is separated into a plurality of compartments by a plurality of spacers, and a steam communication port is provided at the upper part of each spacer to enable the steam to communicate between adjacent compartments, and a cooling fluid communication port is provided at the lower part of each spacer, to enable the cooling fluid to communicate between adjacent compartments.
 6. The waste gas purification apparatus according to claim 4, wherein the cooling chamber is separated into a plurality of compartments by a plurality of spacers, and a steam communication port is provided at the upper part of each spacer to enable the steam to communicate between adjacent compartments, and a cooling fluid communication port is provided at the lower part of each spacer, to enable the cooling fluid to communicate between adjacent compartments.
 7. The waste gas purification apparatus according to claim 3, wherein the cooling chamber is separated into a plurality of compartments by a plurality of spacers, and a steam communication port is provided at the upper of each spacer to enable the steam to communicate between adjacent compartments, and lower parts of the compartments are separated from each other to enable the compartments contain different kinds of cooling fluids and/or cooling fluids with different temperatures for subsection cooling of the waste gas.
 8. The waste gas purification apparatus according to claim 4, wherein the cooling chamber is separated into a plurality of compartments by a plurality of spacers, and a steam communication port is provided at the upper of each spacer to enable the steam to communicate between adjacent compartments, and lower parts of the compartments are separated from each other to enable the compartments contain different kinds of cooling fluids and/or cooling fluids with different temperatures for subsection cooling of the waste gas.
 9. The waste gas purification apparatus according to claim 1, wherein a pumping device is provided between the dust eliminating unit and the absorbing unit, which is used to pump the waste gas output from the dust eliminating unit to the inside bottom part of the absorbing unit to enable the waste gas to be released under the level of the absorbing fluid.
 10. The waste gas purification apparatus according to claim 1, wherein the apparatus comprises a plurality of said absorbing units provided in series.
 11. The waste gas purification apparatus according to claim 10, wherein a pumping device is provided between adjacent absorbing units, which is used to pump the waste gas output from a former absorbing unit to the inside bottom part of a latter absorbing unit to enable the waste gas to be released under the level of the absorbing fluid contained in the latter absorbing unit.
 12. The waste gas purification apparatus according to claim 1, wherein the absorbing unit is provided with an absorbing fluid refreshing device for removing the precipitates in the absorbing unit and for recharging absorbing fluid into the absorbing unit.
 13. The waste gas purification apparatus according to claim 1, wherein the absorbing fluid is alkaline solution.
 14. The waste gas purification apparatus according to claim 1, wherein the apparatus further comprises a waste gas tank provided at the upstream side of the waste gas cooling unit, which is used to let the waste gas rest therein to remove large dust particles contained in the waste gas before the waste gas is supplied to the waste gas transmission pipe.
 15. A waste gas purification method comprising: a cooling step for cooling the waste gas; a dust eliminating step for eliminating harmful substances and dust contained in the waste gas after the waste gas is processed in the cooling step; an absorbing step for eliminating carbon dioxide and sulfide contained in the waste gas after the waste gas is processed in the dust eliminating step; and a purifying step for eliminating harmful substances and dust remained in the waste gas after the waste gas is processed in the absorbing step.
 16. The waste gas purification method according to claim 15, wherein the cooling step further comprises a steam recycling step for recycling the steam generated in the cooling step.
 17. The waste gas purification method according to claim 16, wherein the absorbing step further comprises an absorbing fluid purifying step for removing precipitates generated in the absorbing step and for recharging absorbing fluid.
 18. The waste gas purification method according to claim 15, wherein the method further comprises a resting step for letting the waste gas rest to remove large dust particles contained in the waste gas before the waste gas is processed in the cooling step.
 19. The waste gas purification method according to claim 16, wherein the method further comprises a resting step for letting the waste gas rest to remove large dust particles contained in the waste gas before the waste gas is processed in the cooling step.
 20. The waste gas purification method according to claim 17, wherein the method further comprises a resting step for letting the waste gas rest to remove large dust particles contained in the waste gas before the waste gas is processed in the cooling step. 